Information flow analysis in a discrete-time process algebra

Some of the non-interference properties studied in (Focardi, 1998; Focardi and Gorrieri, 1995) for information flow analysis in computer systems, notably BNDC, are reformulated in a real-time setting. This is done by enhancing the Security Process Algebra of (Focardi and Gorrieri, 1997; Focardi and Martinelli, 1999) with some extra constructs to model real-time systems (in a discrete time setting); and then by studying the natural extensions of those properties in this enriched setting. We prove essentially the same results known for the untimed case: ordering relation among properties, compositionality aspects, partial model checking techniques. Finally, we illustrate a case study of a system that presents no information flows when analyzed without considering timing constraints. When the specification is refined with time, some interesting information flows are detected.